The invention relates to a module for interfacing the end of a fiberoptic cable with an electronic circuit for receiving or transmitting optical signals, and more particularly to such a module having a multipin housing made of nonconductive material. That electronic circuit interconnects leads of an optoelectronic device (photodiode or light emitting diode) with multiple connector pins protruding from the housing.
For such an interfacing module, it is common practice to provide a receptacle for receiving a ferrule at the end of the fiberoptic cable that supports the polished end of the optic fiber, and to spring load the ferrule in a connector at the end of a fiberoptic cable so that the polished end of the fiber will be properly positioned within the receptacle as determined by a stop in the receptacle. Once the connector is inserted into the receptacle, the polished end of the optic fiber will stop in front of a window in the optoelectronic device passing through and supported by an end wall of the housing. The fiberoptic connector and receptacle are normally provided with some means for locking the two together, usually by pushing the connector into the receptacle and turning it less than a quarter of a turn before releasing the connector.
The optoelectronic device may be contained in an enclosure, such as a TO metal can, and typically the enclosure has three or four pins protruding from its base. One is used as a positive lead (+), another as a negative lead (-), and the remaining one or two are used as ground leads. All of these optoelectronic device leads are connected to a circuit board. The electrical signal on the positive and negative leads is generally so small that extreme care must be taken to make the leads as short as possible and to shield them properly so they will not pick up electromagnetic interference (EMI), since even a small amount of EMI may so mask an electrical signal, particularly in the case of a receiver, as to render information being conveyed unreliable, particularly in the case of a photodetector being connected to a circuit board that normally has signal conditioning circuits for processing the electrical signal received before the information is to be used in an electronic system.
The tendency is to house a fiberoptic receiver or transmitter in a multipin housing made of metal, as disclosed in U.S. Pat. No. 4,647,148, for example. While such a metal housing will provide electromagnetic interference (EMI) shielding for the optoelectronic device leads and circuit, there are other problems that need to be addressed, such as size and cost. The problem of size becomes more critical as the `footprint` area that can be devoted to the multipin module housing decreases, and the functions expected of the signal conditioning circuit within the housing increases. Another problem is to have the optoelectronic leads as short as possible in order to minimize sensitivity of the leads to electromagnetic radiation of high frequency components in the circuit contained within the housing, and to minimize distributed capacitance of the leads since signal response of the leads is inversely proportional to capacitance.